Abstract
TWELVE discourses given by scientists and economists of the first rank were delivered at a symposium arranged by the American Philosophical Society to discuss “Atomic Energy and its Implications” ; they have now been published*. Four of these are purely physical: “Fifty Years of Atomic Physics”, by H. D. Smyth ; “Resonance Reactions”, by E. P. Wigner ; “Problems and Prospects in Elementary Particle Research”, by J. A. Wheeler ; “Methods and Objectives in the Separation of Isotopes”, by H. C. Urey. One by R. S. Stone deals with the health protection activities of the plutonium project. E. Fermi contributes a fascinating account of the development of the first chain-reacting pile, leading up to the historic event of December 2, 1942, when on the removal of about eight feet of the last cadmium strip, “the [neutron] intensity started rising slowly, but at an increasing rate, and kept on increasing until it was evident that it would actually diverge”. Nuclear energy had for the first time been produced in appreciable quantities under human control. Fermi says that this first successful pile in the squash court at Chicago University proved exceedingly easy to control. “All the operator has to do is to watch an instrument that indicates the intensity of the reaction and move the cadmium strips in if the intensity shows a tendency to rise and out if the intensity shows a tendency to drop.”The strips operate by absorbing neutrons which would otherwise multiply by causing fission in uranium nuclei, and so preventing the chain reaction from becoming diverging.
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THOMSON, G. ATOMIC ENERGY AND ITS IMPLICATIONS. Nature 157, 826–827 (1946). https://doi.org/10.1038/157826a0
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DOI: https://doi.org/10.1038/157826a0